Waveguide switch

ABSTRACT

A double-throw microwave switch comprising three like, symmetrically-arrayed, Y-shaped waveguide sections. An arm of each of a first and second Y-shaped waveguide section comprises a respective first and second arm of a third one of the three Yshaped waveguide sections, and a third arm of the third Y-shaped waveguide section comprises a common port. A third arm of each of the first and second waveguide sections forms a respective one of a first and second switched port. Electrically switchable impedance means interposed in the waveguide sections selectively couples an alternative one of the first and second ports in microwave circuit with the common port.

United States Patent 191 Carlise Oct. 23, 1973 [54] WAVEGUIDE SWITCH 3,402,369 9/1968 Horiguchi et al. 333/7 D [75] Inventor: lclzlmizrt Lmcoln Carlise, Costa Mesa, Primary Examiner paul L. Gensler Attorney-L. Lee l-lumphries et al. [73] Assignee: North American Rockwell Corporation, El Segundo, Calif. [57] ABSTRACT [22] Filed: Apr. 17 1972 A double-throw microwave switch comprising three like, symmetrically-arrayed, Y-shaped waveguide sec- PP N04 244,815 'tions. An arm of each of a first and second Y-shaped waveguide section comprises a respective first and 52 us. Cl. 333/7 1), 333/98 s arm third one three P wave- 51 Int. Cl. H01p 1 10 guide Swims and a third arm the third Shaped 58 Field of Search 333/7 D, 98 s, '97 s Waveguide Seem" mPrises a P"- A third arm of each of the first and second waveguide sections [56] References Cited forms a respective one of a first and second switched UNTED STATES PATENTS port. Electrically switchable impedance means interposed in the waveguide sections selectively couples an 2 g l g 'ii 32 7 D alternative one of the first and second'ports-in micro- 3l95074 711965 gg 3 3 wave circuit with the common port. 3,321,717 5/1967 Harper 333/7 D 4 Claims, 2 Drawing Figures I lZq ,-l0

ALTERNATE END- FED ANTEVNNA ARRAY 'lzn ,20 GATED BIAS SOURCE GATED BIAS 2| some:

SWITCHING Loon:

SHHII 10F 2 U858 OPEO WAVEGUIDE SWITCH BACKGROUND OF THE INVENTION The technological field to which the subject invention relates is microwave switching means for selectively coupling a common port in microwave circuit with an alternative one of two ports.

In the design of microwave feeds, it is frequently desired or necessary to be able to switchably connect different ports or terminals of a multi-port waveguide arrangement. For example, in an electronically-scanned antenna array, an increased angular scanning range may be effected by alternatively applying the microwave feed to an opposite end of the array in a subsequent scan cycle or mode. Thus, when the array is fed from one end thereof, the scan angle may correspond to the range B, while switching the feed point to the opposite end of the array during a subsequent scan cycle may correspond'to the range 0+3", whereby the total scan angle range achieved is doubled: $8?

In the prior art of switchable microwave feeds, combinations' of non-reciprocal devices, such as ferrite circulators, have been employed in combination with varactor diodes within a multiport waveguide structure. Switching the bias applied across the-diode switches the diode between a reflective shorting impedance and a matched impedance condition forintercoupling different portsof the waveguide assembly by means of different ones of the circulators, as is described more fully in US. Pat. No. 3,205,493 to A. E. Cohen for.Microwave Switch. '1

A disadvantage of such arrangement is the energy attenuation introduced by means of the circulators employed. Also, the asymmetrical microwave circuit achieved by such means results in non-symmetrical performance of the utilization means. Further, where switchable ferrite circdlators'have been utilized, as to avoid the use of the diodes, switching control power supplies of substantially higher power ratings are required. Moreover, the switching speeds of such latter switching devices are severely limited.

BRIEF DESCRIPTION OF THE INVENTION By means of the concept of the subject invention, the above-noted shortcomings of the prior art are avoided and there is provided microwave circuit double-throw switching means which is symmetrical in arrangement and function and which does not employ ferrite circulators or other non-reciprocal impedance means.

In a preferred embodiment of the invention there is provided three like, symmetrically-arranged Y-shaped waveguide sections, a firstarm of each of a first and second Y-shaped waveguide section comprising a respective first and second arm of athird one of said threeY-shaped waveguide sections. A third 'arm of the third Y-shaped waveguide section comprises a common port, while a third arm of each of the first and second Y-shaped waveguide sections forms arespective first and second switched port. There is also provided electrically switchable impedance means interposed in common port.

1 the concept of the invention may be advantageously the waveguide sections for selectively coupling. an alv Accordingly, an object of the subject invention is-to provide an improved double-throw microwave switch.

Another object of the invention is to provide a microwave switch which is reciprocal in operational mode. A further object is to provide a reciprocal switch having low insertion losses.

These and other objects of the invention will become apparent from the following description, taken together with the accompanying drawings, in which:

' BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of a system in which employed; and

FIG. 2 is a plan view of a schematic arrangement of the microwave device of FIG. 1 and in which certain geometrical features thereof are further illustrated.

. In the figures, like reference charactersrefer to like parts-.

, DESCRIPTION OF THE PREFERRED f EMBODIMENTS Referring now to FIG. 1, there isillustra-ted a schematic 'diagram' of a" system in which the microwave switching concept of the invention may be advantageously employed. There is provided an end-fed phasecontrolled radiating array 10 in cooperation with phase control logic 14. By preselectively phase biasing the phased array by an amount [3/2 corresponding to the scan angle range obtainable from the device (when fed from one of terminii 12d and 12b), the device can be made to scan from 0 to +B. Then, by employing the other of terminii l2a and 12b, the array can be made to oppositely scan from 0 to 13. Thus, by switching thefeedpoint of port@ in FIG. 1 between terminii 12a and 12b for successive scan intervals of scanning logic 14, the scan angle range of antenna 10 is doubled or increased to 013, a total excursion of /2B/.

Such switching is accomplished byswitching means having afirst and second port (D and coupled to a respective one of feed terminals 12a and 12b, and further having a common port @which is internally coupled to'an alternative' one of ports@and@in response to the cooperation of switching logic 14. Port is adapted to be externally coupled-to utilization means such as a radar receiver and transmitter, as is well understood in the art.

In cooperation with switching logic 14 may be a flipflop 15 or other two-stage signalling device for gatingon an alternative one of two bias voltage sources 16 and 17. There is also provided in the arrangement of the double-throw microwave switch of FIG; 1, three like symmetrically arrayed Y-shaped waveguide sections 13a, l3b and 130, an arm 14a and 14b of each of first and second Y-shaped waveguide sections 134 and 13b comprising a respective first and second arm .of a third one of the three Y-shaped waveguide sections, a third arm of the third Y-sha ed waveguide 13c section comprising common port A third ann 16a and 16b of each of first and second waveguide sections forms a respective one of the first and second switched ports@and@, and a second arm 15a and 15b of each of the first and second waveguide sections includes a non-reflective load impedance 22a and 22b near a respective terminus thereof. There is also provided electrically switchable impedance means interposed in the waveguide sections for selectively coupling an alternative one of first and second portsand in microwave circuit with common port@.

Such switchable impedance means comprises first switchable impedance means 17a interposed in said first Y-shaped waveguide section 13a for intercoupling said first and common ports and @during an excited first state of such first switchable means, and isolating common port@ from first port @during an unexcited second state of such first switchable means (supplied by gated source 20). There is further included second switchable impedance means 17b interposed in second Y-shaped waveguide section 13b for intercoupling second and common ports state of said second switchable means, and isolating common port from second port (2) during an unexcited second state of second switchable means 171; (supplied by gated source 21). In normal operation, first and second switchable means 17a and 17b are adapted to be synchronously operated in mutually exclusive states.

Each of the above described first and second switchable impedance means comprises a first cavity-tuned diode interposed in a respective one of arms 14a and 1412 (being that arm of each of first and second wave guide sections 13a and 13b which is common to third Y-shaped waveguide section 13c) and situated near a star junction 180 of third waveguide section 16c. Each switchable impedance means further includes a second cavity-tuned diode 19a and 19b interposed in the second arm 15a and 15b of a respective one of first and second waveguide sections 13a and 13b and situated between the load impedance thereof and a star junction @and@during an excited first 18a and 18b of the respective one of the first and sec- 7 as a matched impedance in an excited state thereof and further functions as a reflective short circuitin an unexcited state thereof, first and second diodes (l7a'and 19a) or (17b and 19b) of each of said first and second waveguide sections being adapted to be operated in mutually exclusive states, and respective first diodes (l- 7a and 17b) of first and second waveguide sections 13a and 13b being adapted to be operated in mutually exclusive states.

Thus, in a first state of switching logic 14', diodes 17a and 19b (in cooperation with gated bias source 20) serve as matched impedances within the waveguide structure, while unexcited diodes 19a and 17b comprise normally capacitive short circuits or reflective impedances. In this way, ports and are intercoupled by means of diode 17a and any energy exiting from star junction 18a down arm 15a is reflected back by diode 19a, and any energy exiting star junction 18c down arm 14b is reflected back by diode 17b. In such unexcited state, diode 17b also serves to isolate port from port @and any energy at junction 18b will tend to be dissipated by the load impedance in arm 15b via matched diode 19b.

From the symmetry of the arrangement of element 13 in FIG. 1 (shown more clearly in FIG. 2), it is to be appreciated that, in a second state of logic 14, alternatively allowing source 21 to excite diodes 17b and 19a while removing excitation from diodes 17a and 1%, results in intercoupling ports @and @and in isolating port (D from port Further details of the cavity-tuned diode arrangement within microwave switch means 13 of FIG. 1 are shown in FIG. 2. In order for most efficient functioning of the above described arrangement, it is necessary that the cavity tuned diodes by properly located within the waveguide structure for the particular microwave frequency or wavelength energy to be controlled. Accordingly, it has been determined that for a waveguide arrangementof .86Agspacing between star junction 18c and each of star junctions 18a and 18b, each of diodes 17a and 17b should preferably be located at a distance of 18kg from star junction 19c, and that diodes 19a and 19b should each be located within a respective one of arms 15aand 15b such that the short circuit condition thereof is reflectively matched to a respective one of junctions 18a and 18b, a center-to-center distance of 18kg being utilized between diode and junction in the illustrated geometry of FIG. 2. The dimension of .68kg between star junction 18a and 18b and a respective one of diodes 17a'andl7b allows the'setting up ofa short circuit condition between such respective diode and junction. 1

In an exemplary device, constructed to thedimensions illustrated in FIG. 2, an isolation factor as great as 40db has been obtained between port and a switched-off one of ports@ and@, and a transmission loss of less than 0.7db observed between port and a switched-on one of ports @and@. Because of the symmetrical waveguide arrangement and avoidance of non-reciprocal impedances, a'structure of low cost and weight is obtained.'Also, no more than 0.10 watt is required to operate the four pin diodes employed in switching the five-port microwave structure, which arrangem ent may handle up to IOKW peak of microwave energy at 0.00l duty cycle. The commercially available tion, both the receiver and the transmitter magnetron of a utilizing low-power radar, when turned off, are protected from damage by external high power energy sources to which the antenna in FIG. 1 may be exposed.

Accordingly, there has been described an improved double throw microwave switch of reciprocal nature.

Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of this invention being limited only by the terms of the appended claims.

I claim:

1. A double-throw microwave switch having a first and second switched port and a common port and comprising three like symmetrically-arrayed Y-shaped waveguide sections,

a first arm of each of a first and second Y-shaped waveguide section comprising a respective first and second arm of a third one of said three Y- shaped waveguide sections, a third arm of said third Y-shaped waveguide section comprising said common port, a third arm of each of said first and second waveguide sections forming a respective one of said first and second switched ports, electrically switchable impedance means interposed in said first and second arms of each of said first and second Y-shaped waveguide sections for selectively coupling an alternative one of said first and second ports in microwave circuit with said common port, said switchable impedance means comprising first switchable impedance means interposed in said first Y-shaped waveguide section for intercoupling said first and common ports during a first state of said first switchable means and iso lating said common port from said first port during an unexcited second state of said first switchable means; and p i second switchable impedance means interposed in said second Y-shaped waveguide section for inter-coupling said second and common ports during a first'state ofsaid second switchable means and isolating said'common port from said second port during an unexcited second state of said second switchable means flip-flop means for'synchronously operating said first and second switchable means in mutually exclusive states.

2. The device of claim 1 in which there is included a non-reflective load impedance in a second arm of each of said firstand second waveguide sections, and in which said switchable impedance means of each of said first and second waveguidesection comprises a first cavity-tuned diode interposed in that arm of each of said first and second wavc guide sections which is common to said third Y-shaped waveguide section and situated near a star junction of said third waveguide section, V second cavity-tuned diode interposed in said second arm of arespective one of said first and second waveguide sections and situated between said load impedance'and a star junction of said respective one of said first and second waveguide sections,

each of said cavity-tuned diodes functioning at the center-frequency of the bandwidth of said waveguide'sections as a matched impedance in an excited state thereof and functioning as a reflective short circuit in an unexcited state thereof,

said first and second diodes of each of said first and second waveguide sections being adapted to be operated in mutually exclusive states,

respective first diodes of said first and second waveguide sections being adapted to be operated in mutually exclusive states.

3. A double-throw microwave switch having a first and second switched port and arcommon port and comprising three like symmetrically arrayed Y-shaped, waveguide sections, a an arm of each of a first and second Y-shaped waveguide section comprising a respective vfirst and second arm of a third one of said three Y- shaped waveguide sections,

a third arm of said third Y-shaped waveguide section com-prising said common port,

5 a third arm of each of said first and second waveguide sections forming a respective one of said first and second switched ports,

' a second arm of each of said first and second waveguide sections including a non-reflective load impedance near a terminus thereof, and

electrically switchable impedance means interposed in said .waveguide sections for selectively coupling an alternative one of said first and second ports in microwave circuit with said common port, said electrically switchable impedance means comprising first switchable impedance means interposed in said first Y-shaped waveguide section for inter- ,coupling said first and common ports during a first state of saidfirst switchablemeans and isolating said common port from said first port during an unexcited second state of said first "switchable means; and i second switchable impedance means interposed in said second Y-shaped waveguide section for intercoupling said second and common ports during a first state of said first switchable means and isolatingsaid common port from said second port during an unexcited second state of said second switchable means, and said first and second switchable means being adapted to be synchronously operated in mutually exclusive states, 7 1 said switchable impedance means of each of said first and second waveguide section comprising a first cavity-tuned diode interposed in that arm of each of said first and second waveguide sections which is common to said third "Yshaped waveguide section and situated near a star junction of said third waveguide section,

a second cavity-tuned diode interposed in said second arm of a respective one of said first and second waveguide sections andsituated between said load impedance and a star junction of said respective one of said first and second waveguide sections,

each of said cavity-tuned diodes functioning at v the center-frequency of the bandwidth of I said waveguide'sections as a matched impedance in an excited state thereof and function 7 ing as a reflective short circuit in an unexcited state thereof,;

said first and second diodes of each of said first and second waveguide sections being adapted to be operated in mutually exclusive states,

respective first diodes of said first and'second waveguide sections being adapted to be oper-ated in mutually exclusive states.

4. A double-throw microwave switch having a first and second switched port anda common port and comprising" symmetrically arrayed Y-shaped wavethree like guide sections,

an arm of each of a first and second Y-shaped waveguide section comprising a. respective first and second arm of a third one of said three Y- shaped waveguide sections,

a third arm of said third Y-shaped waveguide section comprising said common port,

a third arm of each of said first and second waveguide sections forming a respective one of said first and second switched ports,

a second arm of each of said first and second waveguide sections including a non-reflective loadimpedance near a terminus thereof, and

electrically switchable impedance means interposed in said waveguide sections for selectively coupling an alternative one of said first and second ports in microwave circuit with said common port, said electrically switchable impedance means comprising first switchable impedance means interposed in said first Y-shaped waveguide section for intercoupling said first and common ports during a first state of said first switchable means and isolating said common port from said first port during an unexcited second state of said first switchable means; and second switchable impedance means interposed in said second Y-shaped waveguide section for intercoupling said second and common ports during a first state of said first switchable means and isolating said common port from said second port during an unexcited second state of said second switchable means, and said first and second switchable means being adapted to be synchronously operated in mutually exclusive states, said switchable impedance means of each of said first and second waveguide section comprising a first cavity-tuned diode interposed in that arm of each of said first and second waveguide sections which is common to said third Y-shaped waveguide section and situated near a star junction of said third waveguide section, a second cavity-tuned diode interposed in said second arm of a respective one of said first and second waveguide sections and situated between said load impedance and a star junction of said respective one of said first and second waveguide sections,

each of said cavity-tuned diodes functioning at the center-frequency of the bandwidth of said waveguide sections as a matched impedance in an excited state thereof and functioning as a reflective short circuit in an unexcited state thereof,

said first and second diodes of each of said first and second waveguide sections being adapted to be operated in mutually exclusive states,

respective first diodes of said first and second waveguide sections being adapted to be operated in mutually exclusive states,

said star-junctions of said first and second waveguide sections being spaced apart from the star junction of said third waveguide section by a first dimension less than onewaveguide wavelength and more than threequarters of a waveguide wavelength,

said first diode of each of said first and second waveguide sections being located less than one quarter waveguide wavelength from said star junction of said third waveguide section,

said second diode of each of said first and second waveguide sections being located less than one quarter wavelength from the star junction of a respective one of said first and second waveguide sections,

said first dimension corresponding to substantially 0.86 of a waveguide wavelength, and

said locations corresponding to substantially 0. 18 waveguide wavelength. 

1. A double-throw microwave switch having a first and second switched port and a common port and comprising three like symmetrically-arrayed Y-shaped waveguide sections, a first arm of each of a first and second Y-shaped waveguide section comprising a respective first and second arm of a third one of said three Y-shaped waveguide sections, a third arm of said third Y-shaped waveguide section comprising said common port, a third arm of each of said first and second waveguide sections forming a respective one of said first and second switched ports, electrically switchable impedance means interposed in said first and second arms of each of said first and second Yshaped waveguide sections for selectively coupling an alternative one of said first and second ports in microwave circuit with said common port, said switchable impedance means comprising first swiTchable impedance means interposed in said first Yshaped waveguide section for intercoupling said first and common ports during a first state of said first switchable means and isolating said common port from said first port during an unexcited second state of said first switchable means; and second switchable impedance means interposed in said second Yshaped waveguide section for inter-coupling said second and common ports during a first state of said second switchable means and isolating said common port from said second port during an unexcited second state of said second switchable means flip-flop means for synchronously operating said first and second switchable means in mutually exclusive states.
 2. The device of claim 1 in which there is included a non-reflective load impedance in a second arm of each of said first and second waveguide sections, and in which said switchable impedance means of each of said first and second waveguide section comprises a first cavity-tuned diode interposed in that arm of each of said first and second waveguide sections which is common to said third Y-shaped waveguide section and situated near a star junction of said third waveguide section, a second cavity-tuned diode interposed in said second arm of a respective one of said first and second waveguide sections and situated between said load impedance and a star junction of said respective one of said first and second waveguide sections, each of said cavity-tuned diodes functioning at the center-frequency of the bandwidth of said waveguide sections as a matched impedance in an excited state thereof and functioning as a reflective short circuit in an unexcited state thereof, said first and second diodes of each of said first and second waveguide sections being adapted to be operated in mutually exclusive states, respective first diodes of said first and second waveguide sections being adapted to be operated in mutually exclusive states.
 3. A double-throw microwave switch having a first and second switched port and a common port and comprising three like symmetrically arrayed Y-shaped waveguide sections, an arm of each of a first and second Y-shaped waveguide section comprising a respective first and second arm of a third one of said three Y-shaped waveguide sections, a third arm of said third Y-shaped waveguide section com-prising said common port, a third arm of each of said first and second waveguide sections forming a respective one of said first and second switched ports, a second arm of each of said first and second waveguide sections including a non-reflective load impedance near a terminus thereof, and electrically switchable impedance means interposed in said waveguide sections for selectively coupling an alternative one of said first and second ports in microwave circuit with said common port, said electrically switchable impedance means comprising first switchable impedance means interposed in said first Y-shaped waveguide section for intercoupling said first and common ports during a first state of said first switchable means and isolating said common port from said first port during an unexcited second state of said first switchable means; and second switchable impedance means interposed in said second Y-shaped waveguide section for intercoupling said second and common ports during a first state of said first switchable means and isolating said common port from said second port during an unexcited second state of said second switchable means, and said first and second switchable means being adapted to be synchronously operated in mutually exclusive states, said switchable impedance means of each of said first and second waveguide section comprising a first cavity-tuned diode interposed in that arm of each of said first and second waveguide sections which is common to said third Y-shaped waveguide section and situated near a star junction of said third wavEguide section, a second cavity-tuned diode interposed in said second arm of a respective one of said first and second waveguide sections and situated between said load impedance and a star junction of said respective one of said first and second waveguide sections, each of said cavity-tuned diodes functioning at the center-frequency of the bandwidth of said waveguide sections as a matched impedance in an excited state thereof and functioning as a reflective short circuit in an unexcited state thereof, said first and second diodes of each of said first and second waveguide sections being adapted to be operated in mutually exclusive states, respective first diodes of said first and second waveguide sections being adapted to be oper-ated in mutually exclusive states.
 4. A double-throw microwave switch having a first and second switched port and a common port and comprising three like symmetrically arrayed Y-shaped waveguide sections, an arm of each of a first and second Y-shaped waveguide section comprising a respective first and second arm of a third one of said three Y-shaped waveguide sections, a third arm of said third Y-shaped waveguide section com-prising said common port, a third arm of each of said first and second waveguide sections forming a respective one of said first and second switched ports, a second arm of each of said first and second waveguide sections including a non-reflective load-impedance near a terminus thereof, and electrically switchable impedance means interposed in said waveguide sections for selectively coupling an alternative one of said first and second ports in microwave circuit with said common port, said electrically switchable impedance means comprising first switchable impedance means interposed in said first Y-shaped waveguide section for intercoupling said first and common ports during a first state of said first switchable means and isolating said common port from said first port during an unexcited second state of said first switchable means; and second switchable impedance means interposed in said second Y-shaped waveguide section for intercoupling said second and common ports during a first state of said first switchable means and isolating said common port from said second port during an unexcited second state of said second switchable means, and said first and second switchable means being adapted to be synchronously operated in mutually exclusive states, said switchable impedance means of each of said first and second waveguide section comprising a first cavity-tuned diode interposed in that arm of each of said first and second waveguide sections which is common to said third Y-shaped waveguide section and situated near a star junction of said third waveguide section, a second cavity-tuned diode interposed in said second arm of a respective one of said first and second waveguide sections and situated between said load impedance and a star junction of said respective one of said first and second waveguide sections, each of said cavity-tuned diodes functioning at the center-frequency of the bandwidth of said waveguide sections as a matched impedance in an excited state thereof and functioning as a reflective short circuit in an unexcited state thereof, said first and second diodes of each of said first and second waveguide sections being adapted to be operated in mutually exclusive states, respective first diodes of said first and second waveguide sections being adapted to be operated in mutually exclusive states, said star-junctions of said first and second waveguide sections being spaced apart from the star junction of said third waveguide section by a first dimension less than one waveguide wavelength and more than three-quarters of a waveguide wavelength, said first diode of each of said first and second waveguide sections being located less than one quarter waveguide wavelength from said star junction of said Third waveguide section, said second diode of each of said first and second waveguide sections being located less than one quarter wavelength from the star junction of a respective one of said first and second waveguide sections, said first dimension corresponding to substantially 0.86 of a waveguide wavelength, and said locations corresponding to substantially 0.18 waveguide wavelength. 